1. Field of the Invention
This invention relates to a non-aqueous composite gel of a novel structural form and a process for the production thereof, said gel comprising a continuous phase composed of a rubber component, as an elastomer component, and an oil component, and a dispersed phase composed of a high boiling point hydrophilic liquid wherein the rubber component is cross-linked. More particularly, it is concerned with a non-aqueous composite gel which, as a result of the presence of the dispersed phase of the high boiling point hydrophilic liquid particles which are emulsified in the form of an O/O emulsion in the gel structure, has unique physical, mechanical, and chemical characteristics, as compared with conventional gels.
2. Description of the Prior Art
Relatively soft aqueous gels comprising various water-soluble organic polymeric compounds, such as starch, cellulose derivatives, gelatin, casein, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid or polyethylene oxide, are known. In almost all such aqueous gels, the water-soluble polymeric compounds absorb water, swelling the gel, whereby the water forms a continuous phase.
These conventional aqueous gels, however, suffer from the disadvantage that at relatively high water contents the strength of the aqueous gel is lowered and the storage stability is generally poor, and when they are allowed to stand in air, the water contained therein easily vaporizes. Furthermore, they have the defect that when they are stored at temperatures below 0.degree. C., the whole gel freezes, becoming very hard and brittle and, as a result, such gels entirely lose their softness.
Japanese Patent Publication No. 18409/72 discloses the preparation of a highly elastic gel composed of an elastic block copolymer and certain oils or higher fatty acids with the gel produced having good softness and high elasticity. This oily gel, however, has a rubber-like impact resilience; it deforms upon application of stress but returns to its original state upon removal of the stress. Accordingly, it has very poor stress dispersing characteristics, as will be explained in more detail later. Furthermore, although it is stable at room temperature, it is inferior in thermal stability; for instance, at a temperature range of from 80.degree. C. to 150.degree. C., difficulty is encountered in retaining its original shape and dimensions, and the oily gel tends to flow and lose its original shape.
It has also been proposed to obtain a hydrous gel by dispersing water particles in a continuous phase of an oily gel which is prepared by casting a W/O (water-in-oil) emulsion in order to provide good stress dispersing characteristics, as described in Japanese Patent Publication No. 48895/77, corresponding to U.S. Pat. No. 4,102,807. This hydrous gel, however, is not sufficiently satisfactory in thermal stability and other characteristics.
Additionally, a cross-linking type hydrous gel has been proposed having a dispersed phase composed of water particles, as described in Japanese Patent Application (OPI) No. 65785/77 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application")). This gel, however, is not sufficiently satisfactory in that specific cross-linking conditions are required in order to prevent the vaporization of water particles during the cross-linking, e.g., application of pressure in an autoclave.